Drilling fluid



" US. Cl. 252--8.5

3,535,238 DRILLING FLUID Jack H. Kolaian, Houston, Tex., assignor to Texaco Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Apr. 25, 1967, Ser. No. 633,401 lint. Cl. C10m 3/34, 3/26 9 Claims ABSTRACT OF THE DISCLOSURE An aqueous drilling fluid dispersant and a method of drilling wells using said drilling fluid which contains a heterocyclic compound as the dispersant, namely, 4-methyl 7,8 dihydroxycoumarin, 2 methylol 5-hydroxy-1,4- pyrone or S-sulfo-8-hydroxyquinoline.

This invention relates to a novel aqueous drilling fluid for drilling wells through sub-surface formations by means of well drilling tools, and particularly to such an aqueous well drilling fluid having improved dispersibility as a result of containing therein a novel dispersant as hereinafter more fully described. The invention is also concerned with a method of drilling wells employing the novel aqueous drilling fluid.

Drilling fluids, or muds as they are sometimes called, are slurries of clayey solids used in the drilling of wells for tapping underground collections of oil, gas, brine, or water. Such fluids have a number of different functions, the most important of which are to assist in the removal of cuttings from the well, to seal off formations of gas, oil, or water which may be encountered at different levels, to lubricate the drilling tool and drill pipe which carries the tool, and to hold the cuttings in suspension in event of shut-downs in drilling.

An ideal drilling fluid is a thixotropic colloidal system, i.e., a fluid which on agitation of circulation (as by pumping or otherwise), has a measurable relatively low viscosity and is free flowing (not plastic), particularly at high temperatures; but when such agitation or circulation is halted, the fluid sets or gels. The rate of gel formation is such as to permit the cuttings to fall only a short distance before the gel structure is sufficiently strong to support them.

When such a drilling fluid having the proper viscosity, the proper gel rate and proper gel strength is circulated through a well bore, it has a sufficiently high viscosity to carry the cuttings and sand from the bottom of the hole to the surface and it has a gel rate such as to allow the cuttings and sand to settle in a settling pit. On standing in a quiescent state, it develops suflicient gel strength to prevent the settling of the cuttings, sand or weighting material, etc., in the well bore when it becomes necessary to discontinue circulation for any appreciable period of time. Such a fluid is also characterized by its ability to form a mud cake on the borehole wall, thereby assisting in sealing off the traversed formations and inhibiting socalled water loss, i.e., loss of water from the drilling fluid.

One of the principal problems in mud chemistry is the production of suitable drilling fluids having satisfactory dispersibility, and the necessary thixotropic properties discussed above.

In accordance with the present invention the problems of dispersibility in aqueous drilling fluids can be solved by 3,535,238 Patented Oct. 20, 1970 incorporating in an aqueous drilling fluid a heterocyclic compound having the general formula wherein Q is aza or oxa, A is a carbonyl oxygen, methylol or hydrogen, B is hydrogen, methyl or a carbonyl oxygen, C and D taken together is o-dihydroxybenzo or p-hydroxysulfobenzo, or taken separately C is hydroxy and D is hydrogen; and when A is a carbonyl oxygen, Q is oxa, B is methyl and C and D taken together is o-dihydroxybenzo; when A is methylol, Q is oxa, B is a carbonyl oxygen, C is hydroxy and D is hydrogen; when A is hydrogen, Q is aza, B is hydrogen and C and D taken together is p-hydroxysulfobenzo.

The large circle in the ring is used to denote an aromatic type ring structure.

The term heterocyclic compound as used in the specification and claims is intended to cover any heterocyclic compound meeting the above general formula and having substituents of the prescribed type at the indicated positions on the ring.

More particularly representative heterocyclic compounds of the present invention include 4-methyl-7,8-dihydroxycoumarin, 2-methylol-5-hydroxy-1,4-pyrone and 5-sulfo-8-hydroxyquinoline.

It is surprising that these heterocyclic compounds are effective dispersants when other heterocyclic compounds such as coumarin are ineffective drilling fluid dispersants.

It is known from the article appearing in Zhur. Priklad. Khem. 35, pages 638-647 (1962), Organic Viscosity Reducer in Clay Solutions by D. Tischenko and S. Fleisher (CA, 57, 2491 g, 1962), that the ortho-dihydroxybenzenesulfonic acids, the ortho-dihydroXy-alpha-toluenesulfonic acids and water soluble salts thereof are viscosity reducing agents in clay laden drilling fluids whereas the corresponding metaand para-dihydroxybenzenes including the corresponding sulfonic acid derivatives and water soluble salts thereof are ineffective viscosity reducing agents for aqueous drilling fluids.

The heterocyclic compounds of the present invention may be added to an aqueous drilling fluid in amounts ranging from about 0.1 pound to about 10 pounds per barrel of drilling fluid. In general, it has been found that amounts less than 0.1 pound per barrel do not produce completely satisfactory results in terms of dispersing activity Whereas amounts above about 10 pounds per barrel are economically unattractive and no improved results are obtained therewith. A preferred range for the heterocyclic compounds of the present invention is from about 0.25 to about 5 pounds per barrel of drilling fluid for most consistent results and efficiency.

The heterocyclic compounds employed in the present invention are known compounds and the manner of their preparation is well known in the art.

In the tables, gel strength (Gels) is reported as determined by a shearometer in accordance with the procedure in the American Petroleum Institute publication RP29, results being expressed either as pounds/ square feet or as time in seconds for a tube to settle in the mud (after the mud has stood for zero time and for 10 minutes). If it settles in more than 60 seconds, shear is reported as pounds per hundred square feet. Yield Point (YP) is calculated by subtracting the Plastic Viscosity (PV) from the Fann Viscosity reading at 300 r.p.1n. Plastic Viscosity (PV) is obtained by calculation, subtracting the Fann reading at 300 rpm. from the 600 r.p.m. reading. Apparent Viscosity (AV) is equal to one half of the Fann Viscosity reading obtained at 600 r.p.n1. The fluidity of a mud can be back calculated from these data, the results being expressed in Faun Viscosity at 600 r.p.m. and 300 rpm. for a direct reading viscosimeter.

The properties of the base mud are shown in the tables.

even after a 16 hour period. A modified shale control drilling fluid contains lime and caustic, if needed, but is free from any added water soluble calcium salt. A modified shale control drilling fluid containing lime and the novel dispersants of the present invention will provide the same beneficial results as achieved with the shale control drilling fluid of Weiss and Hall, US. 2,802,783, i.e., stabilizing and hardening the shale formations in contact therewith. This surprising result is accomplished in the absence of the water soluble calcium salt employed by the Weiss and Hall patent to attain the necessary shale control chemistry needed to stabilize and harden the shale formations in contact therewith.

TABLE ll Shearometer gels,

Additional Amount lb./l ft. API additive, Type and type Ap. v1s., lm, W.L. lF, Ca, 'lime Ex. lbs. mud dispersant IV YP Cpe. 0 10 pH cc. cc. (:0. p.p.u1. hrs.

2 0. 5 D 43 2 16 37 16 2. 0 D 12 34 2 15 39 1G 1 LpH.L0w pH mud. 2 D.Coumarin.

The test data set forth in the following tables indicate the surprising advantages of the heterocyclic compounds of the present invention and demonstrate the beneficial results of the same in improving the dispersibility of drilling fluids.

Representative physical properties of drilling fluids both before and after addition of various materials including the heterocyclic compounds of the present invention are shown in the tables. In each example the amount of material or materials added to the base muds, if any, are shown, expressed in terms of pounds of material per barrel of drilling fluid.

The data in the above Table II show that coumarin is not an effective drilling fluid dispersant in low pH aqueous drilling fluid systems as is evidenced by the very high Yield Point, Apparent Viscosity and gel strength values obtained therewith.

I claim:

1. An aqueous drilling fluid containing clay solids dispersed therein and as the dispersant from about 0.1 to about 10 pounds per barrel of drilling fluid of a heterocyclic compound selected from the group consisting of 4-methyl-7,8 -dihydroxycoumarin, 2-methylol-5- hydroxy-1,4-pyrone and 5-sulfo-8-hydroxyquinoline.

TABLE I Shearometer gels, Additional Amount 1b./100 tt. AP additive, Type and type Ap. vis., Pm, W.L. PF, Ca, Time, Ex. lbs. mud dispersant PV YP Cpe. 0 10 pH co. co co. p.p.1n. hrs

1 LpH 3 0.5 A 10 8 0.25 17 8 2 22 5 1G 2 2.5lime ModSC 2.5 A 9 3 16 3 LpH u- 4 1.0 B 9 2 0.25 11 2 2 17 6 16 3a 1. 5 B 16 5 2 18 6 24 4 LpH 0.5 G 9 4 0.25 14 2 2 17 1 16 4a 1.0 NaCl 0 5 O 17 1 lli 1 O C 10 3 0 g5 13 1 2 l5 2 .a 1G

1 LpH.Low pH mud.

2 ModSC.M0dified shale control mud. 3 A.4-methyl-7,8(lihydroxyeoumarin. 4 B.-2-1netliylol-fi-hydroxy l,4-pyrone.

5 C.5Sulf0-8-hydroxyquinoline.

The data in Table I above show that the heterocyclic compounds are effective dispersants in low pH and modified shale control aqueous drilling fluids as is evidenced by the very low Yield Point Values and Low Gel values 2. An aqueous drilling fluid as claimed in claim 1 wherein said heterocyclic compound is 4-methyl-7,8-dihydroxycoumarin.

3. An aqueous drilling fluid as claimed in claim 1 wherein said heterocyclic compound is Z-methylol-S-hydroxy-1,4-pyrone.

4. An aqueous drilling fluid as claimed in claim 1 wherein said heterocyclic compound is 5-sulfo-8-hydroxyquinoline.

5. An aqueous drilling fluid as claimed in claim 1 wherein said heterocyclic compound is present in the drilling fluid in an amount of from about 0.25 to 5 pounds per barrel of drilling fluid.

6. In a method of drilling wells wherein a drilling fluid is passed through the well in contact with earth formations during the drilling operation, the improvement which comprises contacting said earth formations with an aqueous drilling fluid containing clay solids dispersed therein and as the dispersant at least 0.1 pound per barrel of drilling fluid of a heterocyclic compound selected from the group consisting of 4-methyl-7,8-dihydroxy coumarin, 2-methylol-5-hydroxy-1,4-pyrone and 5- sulfo-8-hydroxyquinoline.

7. A method as claimed in claim 6 wherein the heterocyclic compound is 4-methyl-7,8-dihydroxycoumarin.

References Cited UNITED STATES PATENTS 4/1935 Lawton et al. 2528.5 11/1943 Wayne 2528.5

OTHER REFERENCES Tischenko et 211., Organic Viscosity Depressants for Drilling Fluids, article in Journal of Applied Chemistry of the U.S.S.R., vol. 35, No. 3, March 1962, pp. 611 to 619.

HERBERT B. GUYNN, Primary Examiner US. Cl. X.R. 25235 1, 355

mg?" UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,535, 3 Dated October 20th, 1970 Inventorfi) Jack H. Kolaian It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Columns 3 and L, Reverse ositions of Tables I and II. In Table I, in the column headed, "Ca, p.p.m.'

the value "729" should read --720--.

316M213 "RND SEALED m9 971 M) Attest:

Edw mmr. m. Attesting Offioer mllionar of Fame 

